Description:U.S. regulators have launched an investigation into Tesla's electric Model S sedans. This follows three highly publicized fires in six weeks. Two of them resulted after the cars ran over metallic debris that punctured the battery compartment, and that's what regulators will examine. Probes can lead to recalls. The news drove Tesla's high-flying stock lower at the market open, but then it bounced back. It has fallen 37 percent since the report of the first crash October 2nd.(0:56)